1. Field of the Invention
The present invention relates to an image pickup optical lens assembly, and more particularly to an optical lens assembly comprised of five lens elements that constitutes short total length and features good aberration correction that applies to electronic products for the capture of images.
2. Description of the Related Art
As science and technology advance, the development of optical systems used in digital cameras, lenses used in web cameras or mobile phone cameras tends to have a compact design and a low cost, while providing good aberration correction ability, high resolution, and high image quality.
In general, a conventional optical lens assembly of a mini electronic product comes with different designs, including the two-lens, three-lens, four-lens, and five-or-more lens designs. If the image quality is taken into consideration, the optical lens assemblies with the four-lens and five-lens designs have advantages on aberration correction and modulation transfer function (MTF), and the five-lens design having a higher resolution than the four-lens design is applicable for electronic products of high video quality or high pixel requirement.
In the products such as the mini digital cameras, web cameras, and mobile phone cameras, a compact optical lens assembly with a short focal length and a good aberration correction is required. In various five-lens designs, an image pickup optical lens assembly with a fixed focal length and different combinations of positive and negative refractive powers are adopted. As disclosed in Japanese Pat. Publication Nos. JP2006-293042 and JP2005-015521, U.S. Pat. No. 7,826,151, 2010/0254029 and 2010/0253829, a fifth lens element having an inflection point is adopted in the design for shortening the total length, and as disclosed in R.O.C. Taiwan Pat. No. I329755, 201038966, and M332199 and U.S. Pat. Nos. 7,710,665 and 7,502,181, a fourth-lens and a fifth-lens with different refractive powers are used. Although these designs can achieve a good aberration correction, yet it is difficult to improve the modulation transfer function (MTF) performance during the process of miniaturizing the optical lens assembly. In these prior arts, the fifth lens element having an inflection point is adopted to correct the aberration and distortion of images, but the lens elements with a negative refractive power (such as the second lens element and the fourth lens elements) may have insufficient width or depth of field in their allocating of the refractive power. Therefore, the present invention provides a practical and feasible design to shorten the optical lens assembly, while using the refractive power of the five lens elements and the combination of convex and concave surfaces to improve the image quality for the application on compact electronic devices, in addition to the effect of reducing the total length of the optical lens assembly.